On the use of point target characteristics in the estimation of low subsidence rates due to gas extraction in Groningen, the Netherlands.

The subsurface of the north-eastern part of the Netherlands contains
large gas reservoirs that have been taken into production since the
late 1960s. The resulting subsidence has been precisely and reliably
estimated using measurements from repeated leveling campaigns and is
now for the first time unambiguously observed using PS-InSAR. The
subsidence rates are small (< 1 cm/year) and the PS density is
low due to the rural character of the area. Particularly it is
difficult to distinguish the PS deformation components due to gas
extraction from other possibly superposed deformation regimes. Besides
a strict quality description of the estimated parameters, the
characterization of physical PS properties is therefore of major
importance.

In this paper we focus on the interpretation of PS-InSAR deformation
estimates in Groningen by investigating the scattering properties of
the detected PS. Through combining the shape of their complex
spectrum, Signal-to-Clutter (SCR) ratio and estimated heights from
PS-InSAR processing, the nature of the PS is investigated. Important
issues for performing the scatterer characteristics analysis, such as
coregistration and SAR amplitude calibration, are addressed. After
analyzing the effect of temporal and perpendicular baseline and
Doppler frequency variations, the PS-InSAR deformation estimates from
different reflection types are evaluated on their performance for
estimating subsidence due to gas extraction.